Chris Brown used to have to stay away from Karrueche Tran for legal reasons ... now, he's saying what's up to her in the desert -- chatting with his ex at Coachella.

The singer-songwriter was photographed chatting with the actress at the popular music festival in Indio, California Saturday ... both smiling big while taking in the show.

You gotta see these pics for yourself ... the two stars are speaking amicably, leaving quite a bit of distance between them -- with Tran even laughing at something Brown said it seems.

Chris and Karrueche look almost like friends in these photos ... though once upon a time Tran was granted a restraining order against Brown.

We broke the story back in the day ... Tran filed for a restraining order back in 2017 -- claiming Brown "told a few people that he was going to kill me" while also claiming he had "punched me in my stomach twice," and "pushed me down the stairs."

Months after filing, Tran was granted a five-year restraining order against Brown ... though obviously it's now lapsed.

Brown has beefed with several of Tran's boyfriends since the restraining order was granted ... including engaging in a high-profile feud with Migos' Quavo.