Kathina is a Buddhist festival which comes at the end of Vassa, the three-month rainy season retreat for Theravada Buddhists. The season during which a monastery may hold a Kathina festival is one month long, beginning after the full moon of the eleventh month in the Lunar calendar (usually October).
It is a time of giving, for the laity to express gratitude to monks. Lay Buddhists bring donations to temples, especially new robes for the monks.
As the legend goes, thirty bhikkhus were journeying with the intention of spending Vassa with Gautama Buddha. However, Vassa began before they reached their destination and they had to stop. According to Buddha's guidelines for Vassa, mendicant monks shouldn't travel during the rainy season as they may unintentionally harm crops and/or insects during their journey. As such, the monks had to stop.
Afterwards, the Buddha rewarded the monks by demonstrating a way to practice sharing and generosity. A lay disciple had previously donated cloth to the Buddha, so the Buddha now gave that cloth to the group of monks and told them to make it into a robe and then offer it as a gift to one of them. A frame, called a Kathina, was used to spread the robe while it was being made.
Kahtein (Burmese: ကထိန်, from Pali ကထိန) refers to the ceremony during which yellow robes called matho thingan (မသိုးသင်္ကန်း) are offered to the Buddhist sangha, between the first waning day of Thadingyut (သီတင်းကျွတ်, approximately October) and the full moon day of Tazaungmon (တန်ဆောင်မုန်း, approximately November) in the traditional Burmese calendar. During this period, certain rules of the Vinaya are relaxed for monks. Kahtein trees called badaytha bin (ပဒေသာပင်), on which offerings like money are hung, are also offered.
Kathin (Thai: กฐิน) in Thailand (there is also the transcription "Gathin" in use) is the name for the robes of an ordained monk; the ceremony of Kathina is called Thod Kathin (Thai: ทอดกฐิน). The Thai lunar calendar reckons the day after the 11th full moon as Waning 1, Evening, Moon 11 (Thai: แรม ๑ ค่ำ เดือน ๑๑ Raem 1 Kham Deuan 11 ). The presentation of Kathin by the King of Thailand or HM representative is called The Royal Kathin Ceremony and often has been an occasion for one of Thailand's Royal Barge Processions.
Gathin Festival is a traditional Buddhist festival celebrated by villagers in Northeast Thailand (Issan, Isan, Esarn) and Laos(ບູນກັນທີນ). Colorful parades and offering ceremonies at the end of monks´ retreat at local temples. On Owk-Pansa day of the full moon, villagers and city dwellers will go to their local temple for prayers and paying respect to the sacred.