What if the philippines claim sabah again from malaysia?

Question

lease of sabah to the british by the sultan of sulu

Answer 1

Nothing will happen.  The Philippines has no way to enforce a claim....no navy, no air force and an army that's been tied down for decades by a handful of communist/islamist rebels.

Answer 2

The Philippines has a historic right over Sabah since it was once owned by the Sultan of Sulu and was only leased to the British. Thus, the Philippines could validly claim Sabah as part of its territory.  However, Malaysia will file definitely a protest in the UN to solve the issue.