Buttler hurt his right hip while batting in Englands win against Bangladesh, hobbling for the remainder of his knock and passing on wicketkeeping duties to Jonny Bairstow.
He was scheduled to join his teammates during a net session at the Hampshire Bowl on Wednesday and Bayliss said: "Yes, hes fine. Hell be taking part in todays practice fully.
"It was a little bit precautionary the other day. He said he could have kept, but he wasnt really sure if he would be able to run after a high catch," he added.
Asked if Buttler might play as a specialist batsman to lighten his workload in the field, Bayliss kept his options open.
"I havent really thought about it. Well make that decision in the next day or so," the Australian said.
"Well see how he pulls up and how he performs at practice. Im expecting him to play a full part."
Buttler has been in fine form at the World Cup, with scores of 18, 103 and 64 all coming at punishing strike rates.
Should Buttler fail to prove his fitness, Hampshires James Vince would be the likeliest pick in his role as spare batsman.
All-rounder Moeen Ali is also eyeing a return to the team after sitting out the 106-run victory over Bangladesh in Cardiff.
His off-breaks were deemed surplus to requirements in a seam-heavy attack at Sophia Gardens, but he could come back into consideration in Southampton.
Moeen was excused from training on Wednesday after the birth of his new baby daughter Haadiya.
He will rejoin the squad for final preparations on the eve of the game and is available to take on the West Indies.
Fridays game will mark a first outing for Barbados-born Jofra Archer against a West Indies side containing several of his Caribbean friends and peers.
The 24-year-old suggested at the weekend he would be treating the game like any other, but Bayliss believes it would only be normal if the stakes were slightly elevated.
Archer was offered a chance to make it in English county cricket after being overlooked for the West Indies Under-19 World Cup squad in 2015 and a late bid to bring him back into the fold failed after Englands interest became clear.
"Hes looking forward to it, obviously knows a few guys in their team," said Bayliss.
"Its always bragging rights. Both sides of the argument would like to gain the upper hand in that argument. Lets wait and see.
"It will be the first time he has come up against those guys, but I am sure he is wishing to do well. I am not sure he could be any more confident -- he is a confident young man who has fitted into the group very well.
"He is a typical young fast bowler. He wants to bowl fast, he wants to take wickets and that has to be a good thing for England."