RAG vs Fine-Tuning: When to Use Each Approach for Thai Language AI
By Dr. Kobkrit Viriyayudhakorn, CEO & Founder, iApp Technology
One of the most common questions we hear from Thai AI engineers and technical teams is: "Should I use RAG or fine-tuning for my Thai language application?" It's a critical question that directly impacts development costs, performance, maintenance complexity, and long-term scalability.
The answer, as with most engineering decisions, is: it depends. But understanding when to use each approach—and increasingly, how to combine them—can mean the difference between a successful AI deployment and an expensive failure.
This article provides a comprehensive technical comparison of Retrieval-Augmented Generation (RAG) and fine-tuning specifically for Thai language applications, drawing from our experience at iApp Technology deploying both approaches across hundreds of Thai enterprises.
The Core Question: Adapting LLMs for Specific Tasks
Large Language Models (LLMs) like GPT-4, Claude, and Gemini are incredibly powerful general-purpose AI systems. However, for production enterprise applications, you almost always need to adapt them to:
- Domain-specific knowledge: Industry terminology, company policies, product catalogs
- Current information: Events after the model's training cutoff, real-time data
- Style and format: Company writing style, document templates, response formats
- Thai language nuances: Local context, business etiquette, industry-specific Thai terminology
You have two primary techniques to achieve this adaptation:
- Retrieval-Augmented Generation (RAG): Provide relevant context to the model at query time
- Fine-Tuning: Retrain the model on your specific data to change its behavior
Each approach has distinct characteristics, costs, and use cases. Let's dive deep into both.

Understanding RAG (Retrieval-Augmented Generation)
What is RAG?
RAG is an architecture pattern that enhances LLM responses by retrieving relevant information from an external knowledge base and including it in the prompt context.
The RAG Process (Simplified):
-
Indexing Phase (one-time setup):
- Take your knowledge base (documents, PDFs, databases)
- Break into chunks (typically 200-1000 tokens)
- Convert each chunk into embedding vectors
- Store in a vector database (Pinecone, Weaviate, pgvector, etc.)
-
Query Phase (runtime):
- User asks a question
- Convert question to embedding vector
- Search vector database for most similar chunks
- Retrieve top K most relevant chunks (typically 3-10)
- Construct prompt: system instructions + retrieved context + user question
- Send to LLM for answer generation
Simple RAG Implementation Example (Thai Documents):
from openai import OpenAI
from pinecone import Pinecone
import numpy as np
# Initialize clients
client = OpenAI(api_key="your-api-key")
pc = Pinecone(api_key="your-pinecone-key")
index = pc.Index("thai-knowledge-base")
def embed_text(text: str) -> list:
"""Convert text to embedding vector"""
response = client.embeddings.create(
model="text-embedding-3-small",
input=text
)
return response.data[0].embedding
def retrieve_context(query: str, top_k: int = 5) -> list:
"""Retrieve relevant document chunks for query"""
# Convert query to embedding
query_embedding = embed_text(query)
# Search vector database
results = index.query(
vector=query_embedding,
top_k=top_k,
include_metadata=True
)
# Extract text from results
contexts = [match['metadata']['text'] for match in results['matches']]
return contexts
def rag_query(user_question: str) -> str:
"""Answer question using RAG"""
# Retrieve relevant context
contexts = retrieve_context(user_question)
# Construct prompt with Thai language optimization
context_str = "\n\n".join(contexts)
prompt = f"""คุณเป็นผู้ช่วย AI ที่ตอบคำถามโดยอ้างอิงจากเอกสารที่ให้มา
เอกสารอ้างอิง:
{context_str}
คำถาม: {user_question}
กรุณาตอบคำถามโดยอ้างอิงจากเอกสารที่ให้มา หากไม่พบข้อมูลในเอกสาร ให้บอกว่าไม่มีข้อมูล"""
# Generate response
response = client.chat.completions.create(
model="gpt-4o",
messages=[
{"role": "system", "content": "คุณเป็นผู้ช่วยตอบคำถามที่ซื่อสัตย์และแม่นยำ"},
{"role": "user", "content": prompt}
],
temperature=0.7
)
return response.choices[0].message.content
# Example usage with Thai language query
question = "นโยบายการลาพักร้อนของบริษัทคืออะไร?"
answer = rag_query(question)
print(answer)