Can I enter Thailand on a 60-day tourist visa, go to Vietnam, and return on a 30-day visa exemption?

Hi trying to phone the embassy but no luck; so don’t know if someone can help?

Me and a friend both English citezens; We have flights booked from London to Bangkok return for 78days; we are planning to go to vietnam on a return flight from Bangkok at some point during the holiday but I don’t know what would be the best time to go, as far as I understand the visa exemption for Vietnam is 15 days.

So could we come into Thailand on the 60 day tourist visa single entry and stay for around 50 days, then go to vietnam for 2 weeks and return to Thailand and stay for a week in Bangkok on a visa exemption for 30 days? I’m just worried that we wouldn’t be granted a visa exemption given that we would have just been in Thailand for 50 days or so? Would appreciate some advice and help if anyone has had any past experiences of doing this on the new visa scheme.

Alternatively we could go to Thailand for 30 days on visa exemption, then go to vietnam by getting a visa for vietnam for 4 weeks then return to Thailand on another visa exemption for a week or so? Don’t know again if this would be allowed..

Any feedback is appreciated 😎😌