Palm sugar is traditionally the sweetener of choice in various applications in Thai cooking.
One of the challenges in using palm sugar lies in the slightly varying degrees of sweetness from batch to batch. This largely depends on the time when the coconut palm is harvested. This means that the same recipe can yield different results when made by different brands of palm sugar, or different batches of the same brand. I personally solve this problem by using palm sugar in conjunction with brown or white sugar to ensure more consistent results. It’s not traditional, but it works.
The other challenge is the fact that while the most readily available and oft-used form of palm sugar in Thailand (น้ำตาลปี๊บ) often takes on the consistency of natural peanut butter (albeit stickier), the most common form of palm sugar found outside the kingdom looks like large choux puffs and is hard (น้ำตาลปึก). This makes measurement by volume somewhat tough. How does one measure a cup of something that is shaped that way? You can solve that problem by doing what some people do which is to grate the solid palm sugar with a microplane grater just as one would a hunk of hard cheese.
My favorite method (more knuckle-friendly) is to place a few pieces of palm sugar in a microwavable bowl and heat them up on low just until the palm sugar pieces are soft and pliable. You can then scoop out however much you need.