// CH4 มีเทน
var c = ee.FeatureCollection('USDOS/LSIB_SIMPLE/2017').filter(ee.Filter.eq('country_na', 'Thailand'));
              //Map.addLayer(geometry);
var collection = ee.ImageCollection("COPERNICUS/S5P/OFFL/L3_CH4")
  .select('CH4_column_volume_mixing_ratio_dry_air')
  .filterDate('2021-01-01', '2021-12-31');

var vis = {
  min: 1800,
  max: 2000,
  palette: ['black', 'blue', 'purple', 'cyan', 'green', 'yellow', 'red']
};

Map.addLayer(collection.mean().clip(c),vis);
/*
 * Legend setup
 */
// Creates a color bar thumbnail image for use in legend from the given color
// palette.
function makeColorBarParams(palette) {
  return {
    bbox: [0, 0, 1, 0.1],
    dimensions: '100x10',
    format: 'png',
    min: 0,
    max: 1,
    palette: palette,
  };
}
// Create the color bar for the legend.
var colorBar = ui.Thumbnail({
  image: ee.Image.pixelLonLat().select(0),
  params: makeColorBarParams(vis.palette),
  style: {stretch: 'horizontal', margin: '0px 8px', maxHeight: '24px'},
});
// Create a panel with three numbers for the legend.
var legendLabels = ui.Panel({
  widgets: [
    ui.Label(vis.min, {margin: '4px 8px'}),
    ui.Label(
        (vis.max / 2),
        {margin: '4px 8px', textAlign: 'center', stretch: 'horizontal'}),
    ui.Label(vis.max, {margin: '4px 8px'})
  ],
  layout: ui.Panel.Layout.flow('horizontal')
});
var legendTitle = ui.Label({
  value: 'Map Legend: CH4 column volume mixing ratio dry_air (ppm)',
  style: {fontWeight: 'bold'}
});
// Add the legendPanel to the map.
var legendPanel = ui.Panel([legendTitle, colorBar, legendLabels]);
Map.add(legendPanel);
Map.centerObject(c,5.5);
Map.setOptions('SATELLITE');