I'm going to Thailand in November and plan on going to Vietnam for a week or so as well. Is it smart to buy/book tickets in advance or can I keep it open and purchase tickets onec I'm in Bangkok? I'm also planning to buy plane tickets to Phuket and Chiang Mai to save time. Should I buy those in advance as well or is it just as easy to book those once I'm there? Any info. on this is much appreciated. Thanks!