I attempted to highlight "Make your intentions clear,' but for some reason...I was unable to.
The TDA Rules may seem a bit vague, but they do cover these situations:
2: Player Responsibilities
Players should verify registration data and seat assignments, verify they’re dealt the correct number of cards before SA occurs, protect their hands, make their intentions clear, follow the action, act in turn with proper terminology and gestures, defend their right to act, keep cards visible and chips correctly stacked, remain at the table with a live hand, table all cards properly when competing at showdown, speak up if they see a mistake, play in a timely manner, call for a clock when warranted, transfer tables promptly, follow one player to a hand, know and comply with the rules, practice proper etiquette, inform the house if they see or experience discriminatory or offensive behavior, and generally contribute to an orderly event where all players feel welcome.
Every situation is different. If the player is first to ack and moves chips forward, I would consider the action an intent to bet. If the player refuses, I would insist on a min bet. If they did not want to bet, or their intent was to bet more, perhaps they will learn a lesson and announce the amount before moving chips forward. The important issue that you face as a floorperson is to assure that the integrity of the game is secure and players are protected from unethical players. You don't need them in your cardroom.