Five Thai women, led by second seed Ratchanok Intanon, reached the quarter-finals of the US$120,000 SCG Thailand on Thursday.
Nichaon Jindapon beat Kim Hyo-Min of South Korea 21-11, 21-10.
The other four are Nichaon Jindapon, Porntip Buranaprasertsuk, Sapsiree Taerattanachai and Busanan Ongbumrungpan.
There were only three Thai women in the last eight last year.
World No.5 Ratchanok, 18, edged Xiang Aiying of Singapore 21-7, 13-21, 21-13 in the second round last night at Nimitbutr Gymnasium.
She will next meet sixth seed Nichaon who comfortably beat Kim Hyo-Min of South Korea 21-11, 21-10.
Although Ratchanok holds a 2-1 career record over Nichaon, who is 11 places below in the world rankings, it may not be easy for Ratchanok to win this time.
While Ratchanok is recovering from a foot injury, Nichaon, 22, is in a confident mood and has played well since the beginning of the year.
She started the year as No.32 and is now in the top 20 in the world rankings. Her best result was second at the Australian Open.
Nichaon's best result at the Thailand Open was a semi-final spot in 2009.
Third seed Porntip beat Taiwan's Ya Ching-hsu 18-21, 21-18, 21-19 to meet Busanan in the last eight after seventh seed Busanan saw off Lee Jang-Mi of South Korea 21-12, 17-21, 21-17.
World No.13 Porntip is seeking her third straight semi-final appearance at her national Open.
In 2011, she lost to China's Li Xuerui who went on to win the title and last year she was beaten by eventual champion Saina Nehwal of India.
Top seed Nehwal is slated to face Porntip in the semi-finals again this year.
Nehwal needed only 30 minutes to finish off Febby Angguni of Indonesia in straight sets.
The world No.2 will next play Gu Juan of Singapore for a place in the semi-finals.
Last year, Nehwal beat four Thais en route to her triumph, including Ratchanok in the final.
Fifth seed Sapsiree defeated Arundhati Pantawane of India 14-21, 17-21, 21-17 and will next take on fourth seed Hsiao Ma-pai of Taiwan.
In the men's singles, teenager Sitthikom Thammasin continued his good run when he fought back from one set down to edge 16th-seeded Andre Kurniawan Tedjono of Indonesia 20-21, 21-20, 24-22.
After stunning second seed and world No.20 Tommy Sugiarto of Indonesia in the first round, the 17-year-old Thai beat Vladimir Malkov of Russia in the second round before defeating Tedjono.
Top seed Boonsak Ponsana, who is seeking his second Thailand Open title after his success in 2008, needed only 29 minutes to thrash Teck Zhi Soo of Malaysia 21-10, 21-7.
In today's quarter-finals, Sitthikom faces Jen Hao-hsu, the seventh seed from Taiwan, and Boonsak takes on Rajiv Ouseph, the sixth seed from England.
Boonsak and Sitthikom are the only Thais in the men's quarter-finals.
In the women's doubles, reigning champions Saralee Thoungthongkam and Narissapat Lam will take on compatriots Puttita Supajirakul and Sapsiree in the second round.
Top seeds Duanganong Arookesorn and Kunchala Voravichitchakul also cruised into the second round with an easy 21-9, 21-9 win over Taiwan's Hsiao Huanchen and Chia Wen-lai.