The Bangkok government will offer 500,000 people free Wi-Fi access starting Thursday.  The move is part of a pilot project that will provide 15,000 Internet hotspots.  Bangkok's municipal government said the scheme was part of the city's effort to cut back on its energy.  Officials said they hoped residents would drive less if electronic communication was more convenient. The free service is set to last for one year in its initial phase, and will offer only slow 64K connections designed mainly for checking email or sending text messages.