If you haven't signed and acknowledged the change in salary, you're good. The new company can't force you to join them but sounds like they're trying to scare you. If you reject the offer, they might just blacklist you from applying or working for that company again.
They might threaten to sue you but I don't think they have a solid basis (since they changed the salary), and it would be for a very nominal fee. You can read more here: https://asklegal.my/p/company-letter-offer-reject-malaysia.
Kena con during interview, how to escape?, Jumped ship but wrong move