When using the phrase "say piece," there are a few different synonyms that can be used to convey the same message. The first option is to say "speak your mind," which implies that the person is free to express their thoughts and opinions without holding back. Another option is to say "voice your thoughts," which is similar to "speak your mind" but emphasizes the act of verbalizing thoughts rather than emotions. A third option is to say "have your say," which means to take a turn expressing one's ideas or beliefs. Overall, there are various synonyms for "say piece" that highlight the importance of freely sharing thoughts and ideas.