I always get this wonderful red colored tea when I eat out at Thai restaurants but I have yet to find out its name and where I might get some. Can someone help me?

I went to thailand and had alot of lemongrass tea. How do they make it so diffrent (GOOD) tasting?

same concept as the japanses/korean/chinese groceries around manila. except i need one that offers thai groceries. im looking for tea powders.
checked online already.nothing’s listed.
where is main street?