I've spent a total of about 14 months in Thailand across multiple trips and want to give a complete honest picture of what it costs at different levels.

Backpacker tier ($18-25/day): dorm bed in a good hostel, eating street food exclusively, using local tuk-tuks and buses, doing free or low-cost activities (temples, markets, parks). This is entirely viable but requires discipline and comfort with basic accommodation.

Comfortable budget tier ($30-45/day): private room at a guesthouse or small hotel, eating a mix of street food and sit-down restaurants, occasional taxis, occasional paid activities (cooking class, boat trip, national park). This is what I consider the honest 'budget' target for a reasonable quality of life.

Flashpacker tier ($60-80/day): boutique guesthouse or budget boutique hotel, eating at proper restaurants regularly, comfortable transport choices. You're traveling on a budget compared to Western costs but not roughing it.

The geography premium: the south islands (Koh Samui, Koh Tao, Koh Phi Phi) cost 40-60% more than the north for equivalent accommodation and food. If you're on a tight budget, prioritize Chiang Mai, the north, and the Andaman coast (Koh Lanta, Koh Muk) which is less expensive than the Gulf islands.

Seasonal variation: high season (November-February) accommodation prices increase 20-40% in popular areas. The shoulder months of October and March-April are the best value combination of good weather and reasonable prices.