What type of visa will I receive upon my return to Bangkok on February 29th, and can I obtain an extension before my trip to Bali?

When you return to Bkk as a Canadian Passport holder from Laos, you will get a 30 day visa exemption. You can go to immigration to get a 30 day extension. If you leave Thailand after that 30 day extension, you can fly out to a nearby country and return again for another 30 day Visa exemption.

Yes, you can get visa exemption, but please remember that whether or not you are allowed in is up to the immigrations officer at the border. Your story doesn't tell what part of the last 6 months during which the METV was valid you were in the country, but if it's almost the entire time, I wouldn't be betting on a successful return.

Having a flight to Canada in May and requiring then yet another entry to actually reach that would be a concern. I would recommend planning a strategy to avoid missing that flight, i.e. not making it dependent on a second successful visa exempt entry after spending 8 months here.

Your odds would increase if you now spend significant time in other countries and only come back here for that flight. That'd be a story they could buy into. An alternative would be to give up on Bali and get a single entry tourist visa in Laos before returning. Then you can extend it and stay here until well into May. Lastly, if you really want to go to Bali, you could consider moving your flight to Bali. Most carriers flying to Bangkok also fly there. And if not, you could look at Jakarta instead. Changing the flight will cost you a fee (if even possible; it may not) but if possible it could save you the flight.

You will get stamped in visa exempt for 30 days, if Canada is 1 of the countries that gets that. You can extend it 1 time for 30 days. Be prepared to show proof of funds, proof of onward travel, and explain why you did not get another proper visa.That being said you may just get stamped in and waved off, but a friend last week with his wife, got pulled aside and interrogated before being allowed it. It seems the 4000b inside his passport the last time he handed it to them to look at contained all the proper answers they were looking for.

Unless you apply for a visa in Laos, you will get a 30 days visa exemption that can be extended with another 30 days at the local immigration. At some places you only can apply within the last week (Jomtien, Phuket, etc) some give you extension at any time. (Eks Laksi Bangkok)

This is assuming you are carrying a Canadian passport.

You will be given a 30 day visa exemption when you go through immigration which can be extended once by another 30 days.