Between May and early June is a good time to visit NinhBinh to see golden rice. This is also the time which Tam Coc welcomes the most tourists. For tourists, this is also the best time to go combination with shooting "yellow season".
Tam Coc - Bich Dong is located in the complex of Trang An, Ninh Binh Province. With a system of caves, limestone mountains, beautiful rice fields, this place is considered as a "Ha Long Bay on land".
Source: http://pystravel.vn/tin/8538-kinh-nghiem-du-lich-tam-coc-mua-lua-chin.html
https://dulich.chudu24.com/tin-du-lich/kham-pha/chau-a/viet-nam/ninh-binh/ngo-dong-mua-vang-tren-song.html
http://pressonline.vn/khach-tay-ngo-ngang-truoc-ve-dep-tam-coc-mua-lua-chin-p-13752.html