Port have signed national team goalkeeper Kawin Thamsatchanan, the Thai League 1 club announced on Tuesday.
The 31-year-old joins the Klong Toey-based club from Belgium's OH Leuven.
"This is a big deal and a New Year gift for Port fans," said club chairwoman Nualphan Lamsam.
"Tong [Kawin] is a top-quality goalkeeper with professionalism on and off the pitch."
Kawin was the third-choice goalkeeper and played briefly for Thailand who won the AFF Suzuki Cup in Singapore last week.
Nualphan, also manager of the national side, said Kawin must fight for a place in Port's starting line-up with Worawut Srisupa and Rattanai Songsangchan.
One of Thailand's best goalkeepers of his generation, Kawin won four Thai League 1 titles with Muang Thong United from 2009-2016.
Dubbed "Flying Kawin," he joined Oh Leuven, owned by Thailand's King Power Group, which also owns English Premier League side Leicester City, in 2018 and played only 20 games for the Belgian club.
He also had unsuccessful loan spells at his former club Muang Thong and Japan's Consadole Sapporo.
Port also signed two strikers -- Jenrop Phokhee from Police Tero and Adisak Kraisorn on loan from Muang Thong -- for the second half of the Thai League 1 season which begins this weekend.
Port are currently fourth in the Thai League 1 standings, five points behind leaders Buriram United.
Port host second-placed Bangkok United on Sunday in the biggest clash of the weekend.