I cannot remember when was the last time I made a random merit, Sankatana (สังฆทาน), to a monk on birthday, probably, at the Thai temple some years ago. Making merit is a Buddhist way to comfort Thai souls in order to live happily in peace in this life and the next.
The ritual is just to get a set of Sankatana offerings then find a monk in a temple and inform him of your intention. Basically, this should be any monk you come across. If you are not able to ceremonially converse in Pali-Sankrit with the monk, which most cannot, he will lead you all through the process. After the set is handed over, you must slowly pour a small jug of water into a bowl while he is praying for you and finally water a big tree near by.