Funerals for Thai Buddhists can go on for much longer than what you may have seen before in the West. It could last from anything from one week to a year or two. Depending on how close you were to the deceased, you probably won’t be expected to attend every part of the funeral. For the parents of colleagues at work I probably would only attend the cremation on the last day. For relations of friends you probably would attend at least one if not all of the chanting sessions. If you are close to the family then it might be appropriate for you to bring a wreath. Either that or give the family some money in an envelope.