Winatho won her first junior medals at the Asian Junior Athletics Championships, twice finishing as runner-up to Irina Naumenko in 1997 and 1999 in the heptathlon. She made her senior debut at the 1998 Asian Games and she narrowly missed out on a medal, scoring 5630 points for fourth place. She won the gold medal in the heptathlon at the 1999 Southeast Asian Games and won a 400 metres/400 m hurdles double at the following edition in 2001. She was fifth in the 400 m hurdles at the 2002 Asian Games.