How long can a UK national stay in Thailand after entering at 11:05 PM on January 29th?

As a UK national entering Bangkok at 11:05 PM on January 29th, you would technically have 30 days to stay in Thailand. However, while you counted your departure day as February 27th, it's important to remember that both your arrival and departure days count as full days. Thus, you would need to leave by 11:59 PM on February 27th. To maximize your stay, you could wait until after midnight on January 30th to pass through passport control, which would allow you to extend your stay until February 28th.