Ms Yingluck is visiting Japan over April 19-22 to attend the Japan-Mekong Summit in Tokyo.
The prime minister was welcome by Seijiro Hatttori, deputy governor of Fukuoka prefecture, on her visit to the Hakata train station to be briefed on high speed train operations and security on Sunday morning.
She later travelled by Shinkansen bullet train to Kumamoto prefecture to see a local products project and to visit the landmark Kumamoto castle.
Ms Yingluck said she wanted to learn more about development of the local products project after she saw it once when it started, aiming to improve Thai local products and promoting Small and Medium Enterprises (SMEs) businesses.
The prime minister is scheduled to arrive back at Suvarnabhumi Airport before midnight on Sunday.