In RE the visa question:
It's not hard to get an education visa for dive training, but the paperwork has to be completed outside Thailand at a consulate, and it requires the school in Thailand to send some documents for submission as well. Most of us are willing and able to do this for DMTs. You request the visa length that is appropriate for the type of training you want. I have personally only asked for 3-month renewable/extendable visas for DMTs, but zero to hero instructor programmes are at minimum 6-months, so the visa would need to be longer in that case.
The 15-day visa is only issued at land/sea border crossings to tourists who have not obtained a tourist visa ahead of time at a Thai consulate (or who got a single-entry visa and already used it for an earlier entry into the country). Entering Thailand via an airport confers a 90-day visa-waiver in most cases (depending on country of citizenship), and there is no cost involved. A visa-waiver is just a stamp in the passport with a permit-to-stay of a specified length.
The kind of visa John got is obtained at a Thai consulate outside of Thailand. It makes sense to get that visa if you know you will be entering Thailand across a land border--say, coming in from Malaysia or Cambodia, or coming back from a LOB to Burma with plans for a longer stay in Thailand than 15 days.
A multiple-entry stamp in addition to the visa will let you use a visa to enter and leave the country as many times as you like for the duration of your visa without the need to go buy a new visa at a consulate. (This is not possible for visa-waiver stamps, though.)
Visa regulations in Thailand are complex enough to have spawned an entire web-board called ThaiVisa.com Check that site for really detailed information.
It's not hard to get an education visa for dive training, but the paperwork has to be completed outside Thailand at a consulate, and it requires the school in Thailand to send some documents for submission as well. Most of us are willing and able to do this for DMTs. You request the visa length that is appropriate for the type of training you want. I have personally only asked for 3-month renewable/extendable visas for DMTs, but zero to hero instructor programmes are at minimum 6-months, so the visa would need to be longer in that case.
The 15-day visa is only issued at land/sea border crossings to tourists who have not obtained a tourist visa ahead of time at a Thai consulate (or who got a single-entry visa and already used it for an earlier entry into the country). Entering Thailand via an airport confers a 90-day visa-waiver in most cases (depending on country of citizenship), and there is no cost involved. A visa-waiver is just a stamp in the passport with a permit-to-stay of a specified length.
The kind of visa John got is obtained at a Thai consulate outside of Thailand. It makes sense to get that visa if you know you will be entering Thailand across a land border--say, coming in from Malaysia or Cambodia, or coming back from a LOB to Burma with plans for a longer stay in Thailand than 15 days.
A multiple-entry stamp in addition to the visa will let you use a visa to enter and leave the country as many times as you like for the duration of your visa without the need to go buy a new visa at a consulate. (This is not possible for visa-waiver stamps, though.)
Visa regulations in Thailand are complex enough to have spawned an entire web-board called ThaiVisa.com Check that site for really detailed information.