As per Thai custom, no alcohol will be served or sold in Thailand between April 8th to the 10th due to the 9th being the funeral of Princess Bejaratana Rajasuda.
That means you won’t be able to buy alcohol at a supermarket, a 7-11, or be served it in a bar or restaurant.
This, however, is not a ban on alcohol in Thailand it is merely a suggestion by Thai authorities, in order to pay respects to Princess Bejaratana during the period of her funeral. But, you will find in many areas of Thailand it is treated as a ban, meaning alcohol will not be served — period.
If you are staying in a hotel in Thailand, many of the hotels will probably continue to serve alcohol but it would be nice, I think, to go along with the no alcohol rule simply to pay your respects.
Be aware too that all entertainment venues are shut down in Thailand from the 8th to the 10th of April, so you won’t be able to go drinking at a bar or a nightclub either. They will all be closed.
If you would like to personally pay your respects to the princess, Thai authorities are asking that you wear black from the 8th through the 10th as a sign of mourning.
If you have not been in Thailand during a royal funeral before, you may be interested to discover most Thais will wear black during the funeral period for both work and leisure.