While their relationship is often interpreted as a romantic one by fans, the series never explicitly confirms it. The focus of the anime is on Ash's journey to become a Pokemon Master, and while there are many friendships and rivalries, romance is not a major theme.
The writers have chosen to keep the relationship between Ash and May open to interpretation. Some fans may see it as romantic, while others may see it as a strong friendship. The series itself does not provide a definitive answer.