Electricity in Bangkok is NOT expensive. My MEA bill worked out at 4.54 Baht per KWh (unit) last month. Based on your usage, of, apparently, 808 units - if I read you meter correctly - in 4 1/2 months, the charge should be 3,668 Baht (about $112 USD). If I got the decimal wrong, then 10x that at $1,120 is perfectly possible for heavy usage.
Something doesn't add up. You should ask to see the actual bills from MEA and the juristic office water bill.