FACTBOX: What next for Malaysia's Anwar Ibrahim

KUALA LUMPUR (Reuters) - After winning a bigger than expected majority in a by-election on Tuesday, Malaysia's leading opposition politician Anwar Ibrahim needs to move quickly to secure his coalition.

Here's what Anwar has to do next:

Question: What happens now?

Answer: Anwar needs to secure agreement for him to lead the 82-strong opposition group in parliament. He won an endorsement from the Parti Islam se-Malaysia (PAS) a key coalition partner on Wednesday. Anwar is expected to take his seat in parliament on Thursday where he will be appointed leader of the opposition.

Question: What steps would he have to take to win power?

Answer: Anwar has to win at least 30 lawmakers from the ruling coalition to get a simple majority in the 222-seat parliament. He also needs to make sure that he gets enough Malay Muslim MPs to join the opposition alliance as he moves to form a new government by mid-September. Otherwise leaders from PAS, the Islamist party and a key component of Anwar's opposition alliance, may not be at ease with the partnership, which could lead to the collapse of the loose opposition alliance.

Question: Will he be sworn in to parliament this week or could he miss his chance because of a delay until October?

Answer: The parliament speaker has announced on Wednesday that Anwar will be sworn in on Thursday, a news alert service by the Star newspaper said on Wednesday.

Anwar's allies in the opposition alliance have threatened to disrupt Prime Minister Abdullah Ahmad Badawi's presentation of Budget 2009 in parliament on Friday if he is not sworn in by that time.

Question: Why September16?

Answer: Anwar said he plans to bring down the government on September 16 when he wins over enough lawmakers from the ruling coalition.

It was on this date the Malaysian Federation was formed in 1963, bringing together the provinces of Malaya, Singapore as well as Sabah and Sarawak on Borneo island.

Sabah and Sarawak were the stronghold of the ruling coalition when the opposition inflicted heavy losses on it in the March 8 general election.

It is widely expected that the majority of Anwar's defectors would come from the two East Malaysian states.

Question: If his swearing-in is delayed does he risk being stripped of his parliamentary seat because of an intervening conviction for sodomy?

Answer: Anwar can still lead the opposition alliance even with the court case going on. Anwar has said he has a strong alibi in the sodomy case. He has given details of his alibi to the police investigating the sodomy allegation.

(Reporting by Soo Ai Peng and David Chance; Editing by Sanjeev Miglani)