If you’re only transiting through Singapore to Koh Samui, you typically don’t need to complete any forms or apply for a visa for Singapore, as long as your transit is less than 96 hours and you have an onward ticket.

If you’re entering Singapore for travel, you’ll need to complete an electronic entry form. However, if you’re only transiting through Singapore, nothing needs to be completed. As a UK citizen, you don’t need a visa to enter Thailand for tourism purposes for up to 30 days.