{Si Racha, a town in Chonburi Province, Thailand
Amphoe Si Racha, the district surrounding the town

Sriracha F.C., a football club based in Si Racha
Sriracha sauce, a sauce originating from the town, which has become a genericized term for several chilli sauces}

Then what would the addition of the r stand for? Does the r stand for 'from' maybe?