Just to address a common question here. Here's the response from the Thai authorities to this question.
"If your current passport with your visa has expired, you must carry both your old passport (containing the valid visa) and your new passport whenever you travel to Thailand. Immigration officers will refer to your visa on your old passport when processing your entry and stamp your new passport accordingly. In the event that you lose the old passport containing the visa, you will be required to apply for a new visa without exception. Please note that we are unable to transfer a visa from an old passport to a new one."