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KINZEN
KINZEN

Kittipong Khonthong Senior Full-Stack Engineer

I build AI phone and LINE assistantsAI receptionists, Shopify platforms, agent workspaces, developer tools

Production systems, built and run end to end: event-driven TypeScript services on AWS, Shopify platforms, and AI voice and LINE products with guardrails in code.

Email meView CVLinkedIn (opens in a new tab)
Bangkok
Works
Remote first
Open to
Senior and lead roles
Projects through
Vesperwerk

In numbers

A departures board: every figure clatters into place. Point at a row to flip it again.

  1. 7

    years building production systems

    since 2019

  2. 10+

    brands at AnyMind Group, leading a team of 5 to 8 engineers

    Tech Lead, 2022 to 2026

  3. 6,000+

    daily active users on the real-time transactional platform I work on

    confidential client

  4. 500

    real customer messages through the LINE reply pipeline

    July 2026

    AI phone and LINE receptionist for dental clinics

    37

    rule violations in raw model drafts caught by the code checks, mostly overstated claims

    Every final reply passed those checks in this test set.

Selected work

The first two come with illustrated walkthroughs; the others have a summary and more detail below.

AI receptionist for dental clinics

Clinic AI receptionist

An AI phone and LINE receptionist for dental clinics, with code that checks replies against set rules. In pilot; go-live expected October 2026.

Read the case study

  1. Step 1

    A patient writes in

    A message lands on the clinic's LINE. Phone calls reach the same assistant.

    Built with Fastify, Twilio and the LINE Messaging API.

  2. Step 2

    Speech becomes text

    Chats arrive as text and calls are turned into text as the patient speaks, so staff read one conversation.

    Calls run through real-time speech-to-text.

  3. Step 3

    The model writes a draft

    The model drafts a reply. Nothing has reached the patient yet.

    Prompts stay thin; the rules live in code.

  4. Step 4

    The guard blocks a draft that breaks a rule

    Code reads every draft before it goes out. This one makes a diagnosis, so that sentence is blocked.

    In a July 2026 test, 500 real customer messages ran through the LINE reply pipeline: the code checks caught 37 rule violations in raw model drafts, mostly overstated claims, and every final reply passed those checks in this test set.

  5. Step 5

    The checked reply goes out, and is logged

    The patient gets a reply that passed the rules and an offer to book. Staff see the whole conversation in the back office.

    In pilot with a dental clinic, go-live expected October 2026. On a dedicated phone number since July 2026, with gated releases and one-step rollback.

Illustration with sample data

Try it yourself

See an example of the reply check

Pick a sample message to see a model draft, the rule it breaks and the adjusted reply. This example replays prepared text; it does not call a model or contact a real patient.

Clinic inboxScripted illustration. Not live patient data.
  1. Patient

    My back tooth has been throbbing since last night. What painkiller should I take, and how much?

  2. Model draft (not sent)

    Sorry to hear that. Take ibuprofen 400 mg every 6 hours and it should settle down.

    BlockedNames a medicine and a dosedosing-gate

  3. Sent to patient

    Sorry you are in pain. Medicine is something our dentist needs to advise on. Shall I find you the earliest appointment?

Patient message

Agent workspace

Helm

A macOS workspace where Claude Code, Codex, Kimi and Cursor agents work side by side.

  1. Step 01Open a workspacePoint it at a project folder and pick how many agents to run. Nothing is running yet.
  2. Step 02Agents take their seatsFour panes open in a grid. Each gets a call-sign and shows its engine: Claude Code, Codex, Kimi or Cursor.
  3. Step 03They work in parallelEvery pane runs its own agent. They read, edit and run tests at the same time, side by side.
  4. Step 04Work passes between seatsOne agent hands a note straight to another by name, with no copy and paste in between.
  5. Step 05Checks turn greenEach pane reports its own checks, and they are reviewed before the change merges.

Built with: Tauri 2RustTypeScript

Read the Helm case
Animated illustration of a Helm window: four agent panes named Atlas, Nova, Vega and Sable work on a fictional project. Illustration. The workspace, files and messages are fictional.

Read the Helm case

More work

Commerce, a party game, and the tools I build for my own work.

All work

6 projects, sortable and filterable

  • CommerceDeliveredJan 2022 → Mar 2026

    AnyMind EC Platform

    Shopify storefronts, apps and headless builds for 10+ brands, with a team of 5 to 8 engineers I led as Tech Lead for four years.

  • Developer toolsInternal toolJul 2026

    Visual QA harness

    Playwright-based UI verification with geometry checks, interaction crawling and independent AI review.

  • Developer toolsInternal toolJul → Aug 2026

    Cadence

    macOS voice dictation: a native menu-bar shell over a compiled real-time speech engine.

  • GamesLiveAug 2026

    Ronglen

    Thai-first spoken party games for 2 to 8 players, on one device or in online voice rooms.

Experience

Production systems since 2019, newest first.

  1. Apr 2026 → present

    Vesperwerk Co., Ltd.

    Founder and Software Engineer

    A small software studio building AI voice and LINE products with the rules written in code.

    • Built an AI phone and LINE receptionist for dental clinics, now in pilot with a clinic (go-live expected October 2026), with a staff back office on Fastify, Twilio and the LINE Messaging API.
    • Built deterministic code checks for patient-facing replies. In a July 2026 test, 500 real customer messages ran through the LINE reply pipeline: the code checks caught 37 rule violations in raw model drafts, mostly overstated claims, and every final reply passed those checks in this test set.
    • Traced stalled Thai calls to carrier silence suppression and restored audio processing with server-side silence-frame injection; Twilio support confirmed the cause.
    • Operates on Fly.io with SQLite and Litestream backups, gated releases and one-step rollback; production has run on a dedicated phone number since July 2026.
    • Built Helm in Tauri 2, Rust and TypeScript: a macOS agent workspace used daily as the primary development environment.
    • TypeScript
    • Fastify
    • Twilio
    • LINE Messaging API
    • Tauri
    • Rust
    • Fly.io

  2. Apr 2022 → present

    Confidential client

    Senior Full-Stack Developer

    Real-time transactional platform with wallet and ledger (confidential client, NDA), part-time contract.

    • Full-stack and DevOps engineer on a real-time platform with wallet and ledger: 6,000+ daily active users, 18 repositories, web team of up to 13 engineers.
    • Designed a Kafka-fed daily report cache and split reporting into its own autoscaled service, taking heavy queries off the transaction path.
    • Ran production releases on GitHub Actions, Helm and Terragrunt to AWS EKS with SOPS secrets and a hotfix path; reviewed teammates' code and onboarded new engineers.
    • Co-led the 2026 back-office rebuild in Next.js 16 as a static export on Cloudflare Pages with an auth proxy in Pages Functions.
    • TypeScript
    • NestJS
    • Kafka
    • MongoDB
    • Next.js
    • AWS EKS
    • Terragrunt
    • GitHub Actions

  3. Jan 2022 → Mar 2026

    AnyMind Group

    Tech Lead, EC Platform

    Led a team of 5 to 8 engineers on the EC Platform: Shopify storefronts, apps and headless commerce for 10+ brands.

    • Led a team of 5 to 8 engineers delivering Shopify storefronts, apps and headless builds for 10+ brands, including Mizuno Thailand.
    • Built shared storefront and app components that new brand launches reused, and drove storefront performance work.
    • Delivered Shopify integrations using the Admin GraphQL and Storefront APIs, Liquid, metafields and app proxies, alongside Next.js services.
    • Migrated legacy apps to the Shopify Dev Dashboard and upgraded to the January 2026 Admin API.
    • Reviewed code, mentored a mostly junior and mid-level team, ran performance tests and coordinated releases across cross-functional teams.
    • Shopify
    • GraphQL
    • Liquid
    • Next.js
    • TypeScript

  4. Oct 2019 → Jan 2022

    ZyGen Co., Ltd.

    Full Stack Developer

    Full-stack delivery across web apps, data platforms and the infrastructure under them.

    • Delivered React, Next.js, Angular and NestJS applications with GraphQL, MongoDB, SQL Server and Redis, including a LINE LIFF app.
    • Ran delivery infrastructure on Docker, GKE, GitLab CI/CD, Argo Workflows and Azure App Service.
    • Technical lead for the Unique Influencer web platform (React, NestJS queues and cron jobs, MariaDB); earlier, Python NLP classifiers and SAP ABAP.
    • React
    • Next.js
    • Angular
    • NestJS
    • GraphQL
    • MongoDB
    • Docker
    • GKE

AI-assisted engineering

How I build with AI coding agents: a written spec first, a human at every gate, and evidence before anything merges.

  • Spec first

    Architecture, scope and acceptance criteria are set before agent teams build.

  • Human gates

    Trade-offs, production releases and outward actions need my explicit approval.

  • Automate the reversible

    Daily routines, and an overnight loop with a ground-truth gate, reviewer agents and rollback.

  • Evidence before merge

    Tests on the exact commit, screenshot QA, and deterministic filters on LLM output.

Drag the notes around the board.Press and hold a note to move it.

Tools I reach for

The stack behind the systems above, grouped by the job it does.

Six small loops, one per job, on fictional data. Hover or tap a tile to pause it.

01

AI engineering

A caller is heard, answered and checked before the reply goes out.

  • Claude Code
  • Codex
  • Gemini on Vertex AI
  • Anthropic API
  • Real-time speech-to-text
  • LLM evals
02

Backend

An API boots, takes a booking and streams the event to its consumers.

  • TypeScript
  • Node.js
  • NestJS
  • Fastify
  • GraphQL
  • Kafka
  • BullMQ
  • Python
  • Hexagonal and event-driven design
03

Testing and delivery

Every push runs unit and end-to-end tests before it can ship.

  • Playwright
  • Vitest
  • Jest
  • GitHub Actions
  • GitLab CI/CD
  • Helm (Kubernetes charts)
  • Terragrunt
  • SOPS
04

Data and cloud

Rows land, an index answers, the cache hits, the service scales out.

  • MongoDB
  • PostgreSQL
  • Redis
  • SQLite
  • AWS (EKS, MSK, S3)
  • Docker
  • Kubernetes (EKS, GKE)
  • Fly.io
  • Cloudflare
  • Azure
05

Frontend and apps

A booking screen assembles from components and books a slot.

  • React
  • Next.js
  • Vite
  • Tailwind CSS
  • Three.js
  • Phaser
  • Tauri
06

Integrations

A storefront order hands off to a LINE message the customer can act on.

  • Shopify Admin and Storefront APIs
  • Liquid
  • LINE Messaging API
  • LIFF
  • Twilio Media Streams

Play

Four small scenes to touch: my desk at night, the wordmark in gold, a keyboard and a bowl of water.

My desk after hours, in ink. Drag to look around, tap the gold dots, knock things over. The agents, task and caller are fictional.

A hand-drawn 3D desk at night: a wide monitor, a gold desk phone, a notepad, a lamp, two plants and a window over the Bangkok skyline.

About

I'm Kittipong Khonthong, King to most people: a senior full-stack engineer with seven years of production experience across frontend, backend and DevOps. I build systems end to end and keep running them after they ship.

Since 2022 I have worked part-time, remotely, on a real-time transactional platform with wallet and ledger for a confidential client: event-driven NestJS services on Kafka and MongoDB, releases to AWS EKS, and a back-office rebuild in Next.js that I co-led. From 2022 to 2026 I was also Tech Lead for AnyMind Group's EC Platform, leading a team of 5 to 8 engineers that delivered Shopify storefronts, apps and headless builds for 10+ brands, including Mizuno Thailand. Before that I was a full-stack developer at ZyGen, shipping React, Next.js, Angular and NestJS applications on Docker and GKE.

Since April 2026 I run Vesperwerk, a small software studio. Its first product is an AI phone and LINE receptionist for dental clinics, now in pilot with a clinic (go-live expected October 2026). Deterministic checks in code review each reply before it reaches a patient, under rules that block diagnoses, dosing advice and cure claims. I build with teams of AI coding agents in Helm, my own macOS workspace: the spec comes first, and releases wait for my approval.

Education

B.Eng., Computer EngineeringKing Mongkut's Institute of Technology Ladkrabang2015 → 2019

Languages

  • ThaiNative
  • EnglishProfessional working proficiency

Off the clock

Manchester United, cars built for both looks and pace, and a long queue of games.

Contact

Have a system that has to work?

Email is the fastest way to reach me. I read everything and reply myself.

ktpz.dev@gmail.com
Email meView CVLinkedIn (opens in a new tab)
Time in Bangkok
Bangkok ·
Open to: Roles
Senior and lead engineering roles on product teams. Remote first; Bangkok on-site for the right team.
For a role, email me directly.
Open to: Projects
Project work through Vesperwerk: AI voice and LINE assistants with guardrails in code, Shopify storefronts, apps and API migrations, and TypeScript backends and integrations.
For a project, go through Vesperwerk: vesperwerk.com (opens in a new tab)