You can have it, thief.
The Japanese sentence is very natural, and it is almost a set phrase. You cannot replace 泥棒 with any other synonyms.
I found the English translation like a robotic word-for-word. 泥棒 in the Japanese sentence doesn’t mean an actual “thief”. The Japanese sentence is often used when a mom-and-pop shop is offering a special discount for all products on sale.
Tatoeba currently gives the following sentence as a translation:
#42066: You can have it for nothing.
I support this Tatoeba translation posted by CK (an English teacher living in Japan).