Flights in and out of Thailand are often overbooked so it's imperative that you reconfirm ongoing flights as soon as you arrive. Overland travel from Malaysia is also popular and there are four border crossings between Thailand and Malaysia, two on the west coast, one in the centre and one on the east coast. There are plenty of crossing points between Thailand and Myanmar, Laos or Cambodia, but very few border crossings are made - officially, at least. It's legal for non-Thai foreigners to cross the Mekong River by ferry between Thailand and Laos at several points along the river. Travellers tend to prefer Thailand's good bus and train transport anyway.
Trains are comfortable, frequent, punctual, moderately priced and rather slow.
Cars, jeeps or vans can be rented in Bangkok and large provincial capitals. Motorcycles can be rented in major towns and tourist centres. We encourage you to verify any critical information with the relevant authorities before you travel. This includes information on visa requirements, health and safety, customs, and transportation.