I'm looking at plane tickets prices between Canada and Thailand. 2 one-way tickets aren't really more expensive than roundtrip tickets. I'll probably get a one-way ticket. I'm requesting a double-entry tourist Visa right now. Can I have any problems if I don't have the return ticket yet? Maybe when entering Thailand without visa for 30 days I must have an out ticket but it can be toward any surrounding country?

It's better to be aware of any issues before departure.

Thanks in advance

If you have a visa of any type you should have no problems with a one way ticket

If you do NOT have a visa (or an onward ticket within 30 days) there is a strong possibility that you will not be permitted to board your flight to Thailand.

I will probably make roundtrips from Thailand (Bangkok-Sydney-Bangkok for example), and I might want to stay longer in Thailand 30 days without Visa. Will I have any problem flying out of Thailand and then back in?

I will probably make roundtrips from Thailand (Bangkok-Sydney-Bangkok for example), and I might want to stay longer in Thailand 30 days without Visa. Will I have any problem flying out of Thailand and then back in?

If you hold a Thai visa or an outbound airticket you will be fine.