Burma Entry Information
Burma liveaboard dive trips depart from and return to Thailand, usually Phuket, Khao Lak or Ranong. There is normally a short stop at Kauwtaung (Victoria Point) where immigration proceedures are taken care of. During this time guests can disembark the boats to explore the small town's streets or walk up to the temple overlooking the harbour. It is a chance to buy cheap Burmese rum and cigarettes among other things.
Your liveaboard operator will usually sort out the necessary visa paperwork for you as long as you provide them with passport copies. There is a fee payable on the boat for Burma entry which currently stands at US$230 per person.
Burma Tourist Information
Burma liveaboard dive trips depart from and return to Thailand, usually Phuket, Khao Lak or Ranong. There is normally a short stop at Kauwtaung (Victoria Point) where immigration proceedures are taken care of. 
During this time guests can disembark the boats to explore the small town's streets or walk up to the temple overlooking the harbour. It is a chance to buy cheap Burmese rum and cigarettes among other things.
Your liveaboard operator will usually sort out the necessary visa paperwork for you as long as you provide them with passport copies. There is a fee payable on the boat for Burma entry which depends on the length of the trip but is around US$200-250 per person. You should have crisp new US$ bills with you as it is not possible to change money in Kawthaung.
You will need your passport plus 3 copies of your passport's face page and 3 copies of the Thailand entry stamp page. You will also need 4 passport size photos.
Most tourists enter Thailand with an "entry on arrival" visa but if this is not possible from your country you should make sure that you have a multiple entry visa so that you can re-enter Thailand with no problems after your trip.
You cannot stay in Burma after your trip to continue your travels in Burma. You must re-enter Thailand on your liveaboard and then go back to Burma with the correct visa.
Most of the Burma liveaboards include some diving in Thai waters around Similan and Surin. In this case Marine national park fees are required. Currently (2011-12 season) the rates are 400 baht entry to the park plus 200 baht per diving day.
Once in Myanmar territorial waters it is unlikely that you will leave your dive boat except maybe for a BBQ on a deserted beach. Each liveaboard is issued with a government provided "guide" who makes sure that your boat stays in the designated diving areas only.
As your trip will depart from Thailand you can get detailed Thailand Tourist Information here.
Myanmar Tourism
To go or not to go?
Some advocacy groups discourage tourism to Burma which receives severe international critisism for it's human rights records. However more recently Tourism has been promoted by advocacy groups as a method of providing economic benefit to Burmese civilians, and to avoid isolating the country from the rest of the world. Voices for Burma, a pro-democracy advocate group, states, "We believe that small-scale, responsible tourism can create more benefits than harm.
So long as tourists are fully aware of the situation and take steps to maximise their positive impact and minimise the negatives, we feel their visit can be beneficial overall. Responsible tourists can help Burma primarily by bringing money to local communities and small businesses, and by raising awareness of the situation worldwide."
Liveaboard diving in the Mergui Archipelago is a perfect example of small scale responsible tourism and over the last 15 years or so we have seen how tourism cash into Kawthaung (Victoria Point) has improved the quality of life for the Burmese living there.