Is it obligatory to renew the intention of Ihram after stating it and before boarding the means of transportation?

The questioner's ihram is valid, whether he intended ihram and made the talbiyah after bathing or upon boarding the bus. This is because the time for ihram begins after prayer, or when the mount is ready, or when the journey commences. All of these have been authentically narrated from the Prophet, peace and blessings be upon him.