Considered this but due to all the Covid cough, doing a visa run mid holiday would mean we’d also have to do another night in a SHA+ hotel on arrival, a Covid test with medical certificate from somewhere in Vietnam 72 hours before departure, and another Thai special Covid insurance policy (on top of the first and on top of the real insurance policy we get in Oz)I would book flights to give you six weeks in BKK. Then, if VN opens up you can book a cheap cash flight from BKK-VN and back. Failing that, just do a visa run half way through the trip to anywhere that is open.