Thailand has one of the most efficient and affordable domestic travel infrastructures in Asia.

Flights: To jump between Bangkok, Chiang Mai, and the southern islands (Phuket/Krabi), budget airlines like AirAsia, Nok Air, and Thai Vietjet offer daily 1-hour flights usually costing under $40 USD if booked in advance.
Trains: For a more romantic and scenic route, the overnight sleeper trains (particularly the Route 9 train from Bangkok to Chiang Mai) are incredibly comfortable, clean, and offer a quintessential backpacker experience.

Buddhism is highly revered in Thailand, and respecting local customs is mandatory for a smooth trip. When visiting Wats (temples), both men and women must cover their shoulders and knees. Carry a sarong or lightweight pants in your daypack. Always remove your shoes before entering temple buildings, and never point your feet directly at Buddha statues or monks, as feet are considered the lowest and dirtiest part of the body in Thai culture. Furthermore, the Thai Royal Family is highly respected; never speak ill of the monarchy, as strict Lèse-majesté laws are enforced.

Do not shy away from Thai street food—it is the culinary lifeblood of the country! To ensure you stay healthy, apply the "Golden Rule of Street Food": eat where there is a long line of locals. High turnover means ingredients aren't sitting out in the sun. Classic must-tries include Pad Kra Pao (spicy basil pork with a fried egg), Khao Soi (northern coconut curry noodle soup), and Som Tum (fiery green papaya salad).