Whats the best way to post a package from london to phuket in thailand?

i have a couple of books to send to a friend, not super urgent but I would like it to take less than few weeks and not cost too much.

Should i send it royal mail from the u.k. or should I ship it via DHL?

Cost is based on method of shipping and weight. If you mail DHL yes it's the best but the most costly. Sending airmail from the Post Office is not as expensive but does cost a lot, but will get it to Thailand with in 7 to 10 days. Sending ground shipment is the cheapest but will take as long as two months. Go to the post office and check out the price and decide.